On Fri, 22 Feb 2008, Kirk Wallace wrote:
> Another bit I don't understand:
>
> /* STEP 3: allocate shared memory for joystick data */
> js_data = (hal_js_t *) hal_malloc(sizeof(hal_js_t));
> if (js_data == 0) {
> printf( "ERROR: hal_malloc() failed\n");
> hal_exit(comp_id);
> return -1;
> }
>
> hal_js_t is a defined variable type.
> sizeof(hal_js_t) is the memory size of this type.
> hal_malloc(sizeof(hal_js_t)) returns the memory location of this
> variable.
> I don't understand what (hal_js_t *) does. hal_js_t is a type so it is
> similar to (int *)?
hal_malloc returns a (void *) pointer; this would presumably make
subsequent code complain about pointer mismatches, and the compiler
wouldn't know where to look in the data structure for variables like
&(js_data->axis[n]). the (hal_js_t *) casts the returned pointer to the
correct pointer type.
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